Enable PwmOut pins in nano

[giowild]

Would be nice to let app developers configure a pin as PWMOut in Nano. Current Nano firmware thus needs modifications.

Each PWMOut pin may be configured with two parameters:

• period in microseconds, as int
• and duty cicle as percentage: float [0-1]

This configuration should be sent after the pin initialization

	public void onBoardInitEnded() {
		nanoPwmPin.setStatus(BLEGeneralIO.GENERAL_IO_PWM);
                nanoPwmPin.setPeriod(10000000),
                nanoPwmPin.setDutyCicle(0.2),
	}

EXTRA: check if Arduino/Raspberry pins can be set as PWM pins and integrate them too!

[giowild]

Hot to generate a PWMOut for RedBear Nano, from mbed IDE:

#include "mbed.h"

PwmOut led(P0_4);

int main() {
    led.period_ms(10);
    led.write(0.032);
    while(1) {
    }
}